Electronic circuits are used in countless applications, systems, and devices for a variety of purposes. A comparison circuit, which is also known as a comparator, can be used to compare the magnitudes of two analog quantities (such as voltage or current) and to generate an output that indicates the result of the comparison. A comparison circuit can be used in a digital system or device to generate a logic low or logic high output based on the result of the comparison. For example, if a first input is higher than a second input by at least a threshold amount, then the output is generated to indicate a logic high value; otherwise, the output is generated to indicate a logic low value. In certain applications, the inputs to a comparison circuit represent a differential input signal. For such applications, systematic errors in the comparison threshold may arise when performing the conversion from a differential signal to a full-swing logic output signal.
The systematic threshold error associated with a practical comparison circuit is inversely proportional to the gain of certain parts of the circuit, i.e., the gain from the differential input to the input of the first digital logic gate in the comparison circuit. Moreover, the threshold error is directly proportional to the voltage (or current) imbalance at the conversion point from differential input to single-ended output. Thus, one approach for dealing with the systematic threshold error is to increase the direct current (DC) gain (i.e., the low frequency gain) between the differential input and the conversion point, until the threshold error is sufficiently low. Another technique for addressing the threshold error is to alter the threshold of the logic gate (e.g., an inverter) that receives the single-ended output signal. This technique helps to some extent, but it does not dynamically compensate and adjust over variations in process, power supply voltage, or temperature (PVT). Moreover, this approach tends to degrade the static noise margins of the output logic gate.
Accordingly, it is desirable to have an improved comparison circuit that efficiently and effectively compensates for systematic comparison threshold errors and otherwise addresses certain shortcomings of existing and known solutions. Furthermore, other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.